A horse in New Hampshire has been diagnosed with the Eastern Equine Encephalitis virus infection for the first time this year, according to health officials.
The virus was detected in a horse from Northwood, the New Hampshire Department of Health and Human Services said.
The announcement raises the risk level to high for the town of Northwood. Authorities said the surrounding towns of Barnstead, Barrington, Deerfield, Epsom, Nottingham, Pittsfield, and Strafford will increase from low to moderate.
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New Hampshire has seen no EEE infections in humans so far this season. The last human case in the state came in 2014, when there were three cases.
But four people have contracted EEE in Massachusetts so far this year.
EEE is a rare but serious and potentially fatal disease. Symptoms can include fever, headache, stiff neck and sore throat.
Health officials are warning residents of the consequences of being bitten by a mosquito carrying the EEE virus.
"Eastern Equine Encephalitis in particular, can cause serious brain infection and neurologic disease. With the holiday weekend approaching, we want people to enjoy outdoor activities, but it is critical for residents and visitors to take steps to prevent mosquito bites while outdoors, including using an effective repellent against mosquitoes, avoiding the outdoors from dusk to dawn when mosquitos are most active, and wearing long pants and sleeves to cover exposed skin," New Hampshire state epidemiologist Dr. Benjamin Chan said in a statement.